title: Thiepin-fused heteroacenes: simple synthesis, unusual structure, and semiconductors with less anisotropic behavior.
abstract: The simple one-pot syntheses of sulfur-rich thiepin-fused heteroacences with an alkylidene-fluorene framework, THA1 and THA6 (thiepin-fused heteroacene 1 or 6, in which the thiepin is conjugated at both ortho positions with SCH3 or SC6 H13 , respectively), is reported. Based on electrochemical studies and theoretical calculations, their LUMO energies are relatively low (-3.26 eV), and their HOMO and HOMO-1 orbitals are nearly degenerate. The thiepin ring contributes mainly to HOMO-1 and LUMO orbitals, however, HOMO orbitals dominantly reside on thienoacence rings. Within the crystal of THA1, the molecules adopt a herringbone arrangement and multiple intermolecular interactions lead to the formation of a 2D network. Interestingly, THA6 shows totally different intermolecular arrangements. Organic field-effect transistor (OFET) devices show both compounds exhibiting p-type semiconducting behavior. Thin films or microcrystals of THA1 possess relatively high hole mobility. Moreover, the mobilities of the microcrystal of THA1 along three directions are in the same order, thus the hole-carrier transporting within the hexagonal-plane of microcrystal of THA1 exhibits less anisotropic behavior. In comparison, both thin films and microrods of THA6 show low hole mobilities. This agrees well with the intermolecular arrangements and interactions within crystal of THA6. Further theoretical calculations reveal that significant intermolecular electronic coupling among HOMO-1 orbitals and sulfur atoms play an important role in intermolecular electronic coupling for THA1.
authors.affiliation: Beijing National Laboratory for Molecular Sciences, Organic Solids Laboratory, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 (P.R. China).
authors.forename: Zhengxu
authors.initials: Z
authors.lastname: Cai
authors.forename: Hantang
authors.initials: H
authors.lastname: Zhang
authors.forename: Hua
authors.initials: H
authors.lastname: Geng
authors.forename: Zitong
authors.initials: Z
authors.lastname: Liu
authors.forename: Sifen
authors.initials: S
authors.lastname: Yang
authors.forename: Hewei
authors.initials: H
authors.lastname: Luo
authors.forename: Lang
authors.initials: L
authors.lastname: Jiang
authors.forename: Qian
authors.initials: Q
authors.lastname: Peng
authors.forename: Guanxin
authors.initials: G
authors.lastname: Zhang
authors.forename: Jianming
authors.initials: J
authors.lastname: Chen
authors.forename: Yuanping
authors.initials: Y
authors.lastname: Yi
authors.forename: Wenping
authors.initials: W
authors.lastname: Hu
authors.forename: Deqing
authors.initials: D
authors.lastname: Zhang
keywords: density functional calculations; electronic structure; fused ring systems; semiconductors; sulfur